This invention relates to a power circuit and protective circuitry associated therewith for use in billet heating as well as the surface heat treating or melting of a work piece which are induction heating operations.
In the prior art, these operations are performed in a variety of ways. Gas furnaces have been used, but they are generally unsatisfactory as they have a limited capacity, and they do not provide the critical amount of control over the conditions required with some of the processes. As a result of these limitations, certain power circuits have been employed in the prior art. These power circuits, however, also have several major drawbacks. The prior art power circuits are usually very complex and do not have suitable protection for the costly components which due to the high power application are not only very costly but also more likely to be subject to severe transients and failure conditions which could cause their destruction. Furthermore, most of the prior art power circuits are controlled by motor generators which do not provide an adequate mechanism for regulating the variation of power and the general operation of circuit. Nevertheless, despite the complexity of these power circuits and the lack of reliability along with the poor control characteristics they are widely used.